Offshore wind-power producers from Dong Energy A/S to RWE AG are building custom ships at record rates to reduce the cost of the technology which is three times as pricey as electricity from coal plants. As many as 20 vessels, some with movable legs which reach the seafloor, will come onto the market in the next few years, reducing chartering costs of as much as 200,000 euros ($261,000) a day, said Marc Seidel, an offshore engineer at Suzlon Energy Ltd., which supplies turbines to Germany’s RWE. A lack of specialized installation ships has forced companies to hire barges designed for oil exploration, holding up work at projects such as EON AG’s Robin Rigg wind farm off Scotland’s western coast.